An apparatus and method for optimising a communications constellation is provided in which a specification of a communications constellation is received from a user, one or more modules for modellingproperties of the specified communications constellation are selected, properties of the communications constellation are formatted to a common format for integration, the viability of the communications constellation is confirmed by assessing its connectivity, modelled with the integrated formatted properties, and its utility, and the performance of the communications constellation is simulated and optimised by applying one or more test scenarios to the modelled communications constellation. The simulation results are output to the user.